The present invention relates to lamps with light emitting diodes mounted in tubular housings.
With the present energy crisis, it becomes evident that the need for more energy efficient lamps of all configurations need to be developed and implemented as soon as possible for energy conservation.
Many private, public, commercial and office buildings including transportation vehicles like trains and buses, use fluorescent lamps installed in lighting fixtures. Fluorescent lamps are presently much more efficient than incandescent lamps in using energy to create light. Rather than applying current to a wire filament to produce light, fluorescent lamps rely upon an electrical arc passing between two electrodes, one located at either ends of the lamp. The arc is conducted by mixing vaporized mercury with purified gases, mainly Neon and Krypton or Argon gas inside a tube lined with phosphor. The mercury vapor arc generates ultraviolet energy, which causes the phosphor coating to glow or fluoresce and emit light. Standard electrical lamp sockets are positioned inside the lighting fixtures for securing and powering the fluorescent lamps to provide general lighting.
Unlike incandescent lamps, fluorescent lamps cannot be directly connected to alternating current power lines. Unless the flow of current is somehow stabilized, more and more current will flow through the lamp until it overheats and eventually destroys itself The length and diameter of an incandescent lamp""s filament wire limits the amount of electrical current passing through the lamp and therefore regulates its light output. The fluorescent lamp, however using primarily an electrical arc instead of a wire filament, needs an additional device called a ballast to regulate and limit the current to stabilize the fluorescent lamp""s light output.
Fluorescent lamps sold in the United States today are available in a wide variety of shapes and sizes. They run from miniature versions rated at 4 watts and 6 inches in length with a diameter of ⅝ inches, up to 215 watts extending eight feet in length with diameters exceeding 2 inches. The voltage required to start the lamp is dependent on the length of the lamp and the lamp diameter. Larger lamps require higher voltages. A ballast must be specifically designed to provide the proper starting and operating voltages required by the particular fluorescent lamp.
In all fluorescent lighting systems today, the ballast performs two basic functions. The first is to provide the proper voltage to establish an arc between the two electrodes, and the second is to provide a controlled amount of electrical energy to heat the lamp electrodes. This is to limit the amount of current to the lamp using a controlled voltage that prevents the lamp from destroying itself.
Fluorescent ballasts are available in magnetic, hybrid, and the more popular electronic ballasts. Of the electronic ballasts available, there are rapid start and instant start versions. A hybrid ballast combines both electronic and magnetic components in the same package.
In rapid start ballasts, the ballast applies a low voltage of about four volts across the two pins at either end of the fluorescent lamp. After this voltage is applied for at least one half of a second, an arc is struck across the lamp by the ballast starting voltage. After the lamp is ignited, the arc voltage is reduced to the proper operating voltage so that the current is limited through the fluorescent lamp.
Instant start ballasts on the other hand, provide light within {fraction (1/10)} of a second after voltage is applied to the fluorescent lamp. Since there is no filament heating voltage used in instant start ballasts, these ballasts require about two watts less per lamp to operate than do rapid start ballasts. The electronic ballast operates the lamp at a frequency of 20,000 Hz or greater, versus the 60 Hz operation of magnetic and hybrid type ballasts. The higher frequency allows users to take advantage of increased fluorescent lamp efficiencies, resulting in smaller, lighter, and quieter ballast designs over the standard electromagnetic ballast.
Existing fluorescent lamps today use small amounts of mercury in their manufacturing process. The United States Environmental Protection Agency""s (EPA) Toxicity Characteristic Leaching Procedure (TCLP) is used by the Federal Government and most states to determine whether or not used fluorescent lamps should be characterized as hazardous waste. It is a test developed by the EPA in 1990 to measure hazardous substances that might dissolve into the ecosystem. Some states use additional tests or criteria and a few have legislated or regulated that all fluorescent lamps are hazardous whether or not they pass the various tests. For those states that use TCLP to determine the status of linear fluorescent lamps, the mercury content is the critical factor. In order to minimize variability in the test, the National Electrical Manufacturers Association (NEMA) developed a standard on how to perform TCLP testing on linear fluorescent lamps (NEMA Standards Publication LL1-1997).
The TCLP attempts to simulate the effect of disposal in a conventional landfill under the complex conditions of acid rain. Briefly, TCLP testing of fluorescent lamps consists of the following steps:
1. All lamp parts are crushed or cut into small pieces to ensure all potential hazardous materials will leach out in the test.
2. The lamp parts are put into a container and an acetic acid buffer with a pH of 5 is added. A slightly acidic extraction fluid is used to represent typical landfill extraction conditions.
3. The closed container is tumbled end-over-end for 18 hours at 30 revolutions per minute.
4. The extraction fluid is then filtered and the mercury that is dissolved in the extraction fluid is measured per liter of liquid.
The average test result must be lower than 0.2 milligrams of mercury per liter of extraction fluid for the lamp to be qualified as non-hazardous waste. Items that pass the TCLP described above are TCLP-compliant, are considered non-hazardous by the EPA, and are exempt from the Universal Waste Ruling (UWR). Four-feet long fluorescent lamps with more than 6 milligrams of mercury, for example, fail the TCLP without an additive. The UWR is the part of the EPA""s Resource Conservation and Recovery Act (RCRA), which governs the handling of hazardous waste. The UWR was established in May 1995 to simplify procedures for the handling, disposal, and recycling of batteries, pesticides, and thermostats, all considered widespread sources of low-level toxic waste. The purpose was to reduce the cost of complying with the more stringent hazardous waste regulations while maintaining environmental safeguards. Lamps containing mercury and lead were not included in the UWR. Originally, in most states, users disposing more than 350 lamps a month were required to comply with the more stringent government regulations. In Jul. 6, 1999 the EPA added non-TCLP-compliant lamps like those containing lead and mercury to the UWR. This addition went into effect in Jan. 6, 2000. So lamps that pass the TCLP are exempt from the UWR.
Not all states comply with the UWR after Jan. 6, 2000. Individual states have a choice of adopting the UWR for lamps or keeping the original RCRA full hazardous waste regulation. States can elect to impose stricter requirements than the federal government, which is what California has done with its TTLC or Total Threshold Limit Concentration test. In addition to a leaching test, the state of California has a total threshold limit concentration (TTLC) for mercury for hazardous waste qualification. Other states are considering implementing a total mercury threshold as well. California has a more rigorous testing procedure for non-hazardous waste classification. The Total Threshold Limit Concentration (TTLC) also needs to be passed in order for a fluorescent lamp to be classified as non-hazardous waste. The TTLC requires a total mercury concentration of less than 20 weight ppm (parts per million): for example, a F32 T8 lamp with a typical weight of 180 grams must contain less than 3.6 milligrams of mercury. Philips"" ALTO lamps were the first fluorescent lamps to pass the Environmental Protection Agency""s (EPA) TCLP (Toxic Characteristic Leaching Procedure) test for non-hazardous waste. Philips offers a linear fluorescent lamp range that complies with TTLC and is not hazardous waste in California with other lamp manufacturers following close behind.
Certain fluorescent lamp manufacturers like General Electric (GE) and Osram-Sylvania (OSI) use additives to legally influence the TCLP test. Different additives can be used. GE puts ascorbic acid and a strong reducing agent into the cement used to fix the lamp caps to the fluorescent lamp ends. OSI mixes copper-carbonate to the cement or applies zinc plated iron lamp end caps. The copper, iron, and zinc ions reduce soluble mercury. These additives are found in fluorescent lamps produced in 1999 and 2000. The use of additives reduces the soluble mercury measured by the TCLP test in laboratories and is a legitimate way to produce TCLP compliant fluorescent lamps.
Unfortunately, the additive approach does not reduce or eliminate the amount of hazardous mercury in the environment. More importantly, the additives may not work as effectively in the real world as they do in the laboratory TCLP test. In real world disposal, the lamp end caps are not cut to pass a 0.95 cm sieve, are not tumbled intensively with all other lamp parts for 18 hours, and so forth. Therefore, the additives that become available during the TCLP test to reduce mercury leaching may not or only partly, do their job in real world disposal. As a consequence, lamps that rely on additives pass TCLP, but may still have relatively high amounts of mercury leaching out into the environment.
The TCLP test is a controlled laboratory test meant to represent typical landfill conditions. The EPA developed this test in order to reduce leaching of hazardous materials in the environment. Of course, such a test is a compromise between the practicality of testing a large variety of landfill materials and actual landfill conditions. Not every landfill has a pH of 5 and metal parts are not normally cut into small pieces.
The amount of mercury that leaches out in real life will depend strongly on the type of additive used and the exact disposal conditions. However, the xe2x80x9cadditivexe2x80x9d approach is not a guarantee that only small amounts of mercury will leach into the environment upon disposal.
Several states including New Jersey, Delaware, and Arkansas have addressed the additive issue. They have indicated that if lamps with additives were thrown away as non-hazardous waste and are later found to behave differently in the landfill, then the generators and those who dispose of such lamps could potentially face the possibility of having violated the hazardous waste disposal regulation known as RCRA.
The best fluorescent lamps in production at this time include GE""s ECOLUX reduced mercury long-life XL and Philips"" ALTO Advantage T8 lamps. They both have a rated lamp life of 24,000 hours, produce 2,950 lumens, and have a Color Rendering Index (CRI) of 85. Rated life for fluorescent lamps is based on a cycle of 3 hours on and 20 minutes off.
Besides the emission of ultra-violet (UV) rays and the described use of mercury in the manufacture of fluorescent lamps, there are other disadvantages to existing conventional fluorescent lamps that include flickering and limited usage in cold weather environments.
In conclusion, a particularly useful approach to a safer environment is to have a new lamp that contains no harmful traces of mercury that can leach out in the environment, no matter what the exact disposal conditions are. No mercury lamps are the best option for the environment and for the end-user that desires non-hazardous lamps. Also, no mercury LED retrofitting lamps will free many users from the regulatory burdens such as required paperwork and record keeping, training, and regulated shipping of otherwise hazardous materials. In addition, numerous industrial and commercial facility managers will no longer be burdened with the costs and hassles of disposing large numbers of spent fluorescent lamps considered as hazardous waste. The need for a safer, energy efficient, reliable, versatile, and less maintenance light source is needed.
Light emitting diode (LED) lamps that retrofit fluorescent lighting fixtures using existing ballasts can help to relieve some of the above power and environmental problems. These new LED lamps can be used with magnetic, hybrid, and electronic instant and rapid start ballasts, and will plug directly into the present sockets thereby replacing the fluorescent lamps in existing lighting fixtures. The new LED retrofit lamps are adapted to be inserted into the housing of existing fluorescent lighting fixtures acting as a direct replacement light unit for the fluorescent lamps of the original equipment. The major advantage is that the new LED retrofit lamps with integral electronic circuitry are able to replace existing fluorescent lamps without any need to remove the installed ballasts or make modifications to the internal wiring of the already installed fluorescent lighting fixtures. The new LED retrofit lamps include replacing linear cylindrical tube T8 and T12 lamps, U-shape curved lamps, circular T5 lamps, helical CFL compact type fluorescent and PL lamps, and other tubular shaped fluorescent lamps with two or more electrical contacts that mate with existing sockets.
The use of light emitting diodes (LED) as an alternate light source to replace existing lamp designs is a viable option. Light Emitting Diodes (LEDs) are compound semiconductor devices that convert electricity to light when biased in the forward direction. In 1969, General Electric invented the first LED, SSL1 (Solid State Lamp). The SSL1 was a gallium phosphide device that had transistor-like properties i.e. high shock, vibration resistance and long life. Because of its small size, ruggedness, fast switching, low power and compatibility with integrated circuitry, the SSL1 was developed for many indicator-type applications. It was these unique advantages over existing light sources that made the SSL1 find its way into many future applications.
Today, advanced high-brightness LEDs are the next generation of lighting technology that is currently being installed in a variety of lighting applications. As a result of breakthroughs in material efficiencies and optoelectronic packaging design, LEDs are no longer used as just indicator lamps. They are now used as a light source for the illumination of monochromatic applications such as traffic signals, vehicle brake lights, and commercial signs.
In addition, white light LED technology will change the lighting industry, as we know it. Even with further improvements in color quality and performance, white light LED technology has the potential to be a dominant force in the general illumination market. LED benefits include: energy efficiency, compact size, low wattage, low heat, long life, extreme robustness and durability, little or no UV emission, no harmful mercury, and full compatibility with the use of integrated circuits.
To reduce electrical cost and to increase reliability, LED lamps have been developed to replace the conventional incandescent lamps typically used in existing general lighting fixtures. LED lamps consume less energy than conventional lamps and give much longer lamp life.
Unfortunately, the prior art LED lamp designs used thus far still do not provide sufficiently bright and uniform illumination for general lighting applications, nor can they be used strictly as direct and simple LED retrofit lamps for existing fluorescent lighting fixtures and ballast configurations.
U.S. Pat. No. D366,506 issued to Lodhie on Jan. 19, 1999, and U.S. Pat. No. D405,201 issued to Lodhie on Feb. 2, 1999, both disclose an ornamental design for a bulb. One has a bayonet base and the other a medium screw base, but neither was designed exclusively for use as a retrofit lamp for a fluorescent lighting fixture using the existing fluorescent sockets and ballast electronics. Power to the circuit boards and light emitting diodes are provided on one end only. Fluorescent ballasts can provide power on at least one end, but normally power to the lamp is supplied into two ends. Likewise, U.S. Pat. No. 5,463,280 issued to Johnson, U.S. Pat. No. 5,655,830 issued to Ruskouski, and U.S. Pat. No. 5,726,535 issued to Yan, all disclose LED Retrofit lamps exclusively for exit signs and the like. But as mentioned before, none of the disclosed retrofit lamps are designed for use as a retrofit lamp for a fluorescent lighting fixture using the existing fluorescent sockets and ballast electronics. Power to the circuit boards and light emitting diodes are provided on one end only while existing fluorescent ballasts can provide power on two ends of a lamp.
U.S. Pat. No. 5,577,832 issued to Lodhie on Nov. 26, 1996, teaches a multilayer LED assembly that is used as a replacement light for equipment used in manufacturing environments. Although the multiple LEDs, which are mounted perpendicular to a base provides better light distribution, this invention was not exclusively designed for use as a retrofit lamp for fluorescent lighting fixtures using the existing fluorescent sockets and ballast electronics. In addition, this invention was designed with a single base for powering and supporting the LED array with a knob coupled to an axle attached to the base on the opposite end. The LED array of the present invention is not supported by the lamp base, but is supported by the tubular housing itself The present invention provides power on both ends of the retrofit LED lamp serving as a true replacement lamp for existing fluorescent lighting fixtures.
U.S. Pat. No. 5,688,042 issued to Madadi on Nov. 18, 1997, discloses LED lamps for use in lighted sign assemblies. The invention uses three flat elongated circuit boards arranged in a triangular formation with light emitting diodes mounted and facing outward from the center. This configuration has its limitation, because the light output is not evenly distributed away from the center. This LED lamp projects the light of the LEDs in three general zonal directions. Likewise, power to the LEDs is provided on one end only. In addition, the disclosed configuration of the LEDs limits its use in non-linear and curved housings.
U.S. Pat. No. 5,949,347 issued to Wu on Sep. 7, 1999, also discloses a LED retrofit lamp for illuminated signs. In this example, the LEDs are arranged on a shaped frame, so that they are aimed in a desired direction to provide bright and uniform illumination. But similar to Madadi et al, this invention does not provide for an omni-directional and even distribution of light as will be disclosed by the present invention. Again, power to the LEDs is provided on one end of the lamp only and cannot be used in either non-linear or curved housings.
The present invention has been made in order to solve the problems that have arisen in the course of an attempt to develop energy efficient lamps. This invention is designed to replace the existing hazardous fluorescent lamps that contain harmful mercury and emit dangerous ultra-violet rays. They can be used directly in existing sockets and lighting fixtures without the need to change or remove the existing fluorescent lamp ballasts or wiring.
Therefore, it is an object of the present invention to provide a novel LED retrofit lamp for general lighting applications incorporating light emitting diodes as the main light source for use in existing fluorescent lighting fixtures.
Another object of the present invention is to provide such a LED retrofit lamp that can readily replace fluorescent lighting units offering energy efficiency, longer life with zero mercury, zero disposal costs, and zero hazardous waste. The present invention can be used with all types of existing fluorescent ballasts.
Yet another object of the present invention is to provide an improved retrofitting LED lamp for existing fluorescent lamps that will produce a generally even distribution of light similar to the light distribution generated by existing fluorescent lamps.
A further object of the present invention is to provide an improved LED retrofit lamp that can be economically manufactured and assembled, and made adaptable for use in a wide variety of household, commercial, architectural, industrial, and transportation vehicle lighting applications.
A yet further object of the present invention is to provide a LED retrofit lamp containing integral electronic circuitry that can be readily and economically fabricated from simple electronic components for easy adaptation for use with existing electronic, hybrid, and magnetic fluorescent ballasts.
The present invention solves the aforementioned problems with prior inventions by providing a LED retrofit lamp that has a main, generally tubular housing terminating at both ends in a lamp base that inserts directly into the lamp socket of existing fluorescent lighting fixtures used for general lighting in public, private, commercial, industrial, residential buildings, and even in transportation vehicles. The new LED lamps include replacing linear cylindrical tube T8 and T12 lamps, U-shape curved lamps, circular T5 lamps, and CFL compact type fluorescent and PL lamps, etc. The main outer tubular housing of the new LED lamps can be linear, U-shaped, circular, or helical in configuration. It can be manufactured as a single hollow housing or as two halves that can be combined to form a single hollow housing. The two halves can be designed to snap together, or can be held together with glue, or by other means like ultrasonic welding, etc. The main outer tubular housing can be made of a light transmitting material like glass or acrylic plastic for example. The surface of the main outer tubular housing can be diffused or can be coated with a white translucent film to create a more dispersed light output similar to present fluorescent lamps. Power to the LED retrofit lamps in the various shapes and configurations is provided at the two ends by existing fluorescent ballasts. Integral electronic circuitry converts the power from the fluorescent ballasts necessary to power the LEDs mounted to the circuit boards that are inserted within the main outer tubular housing. Desirably, the two base end caps of the retrofitting LED lamp have apertures therein to allow air to pass through into and out from the interior of the main outer tubular housing and integral electronic circuitry.
In one embodiment of the present invention, the discrete or surface mount LEDs are compactly arranged and fixedly mounted with lead-free solder onto a flat rectangular flexible circuit board made of a high-temperature polyimide or equivalent material. There are long slits between each column or row of LEDs. The entire flexible circuit board with the attached LEDs is rolled to form a hollow and generally cylindrical frame, with the LEDs facing radially outward from a central axis. Although this embodiment describes a generally cylindrical frame, it can be appreciated by someone skilled in the art to form the flexible circuit board into shapes other than a cylinder, such as an elongated oval, triangle, rectangle, hexagon, octagon, and so on among many other possible configurations. Accordingly, the shape of the tubular housing holding the individual flexible circuit board can be made in a similar shape to match the shape of the formed flexible circuit board. The entire frame is then inserted inside the main outer tubular housing. It can also be said that the shape of the flexible circuit board can be made into the same shape as the tubular housing. The length of the frame is always within the length of the linear main outer tubular housing. AC power generated by the external fluorescent ballast is converted to DC power by additional integral electronics. Electrical connector means are used to connect the integral electronics to the light emitting diode array and to provide current to the LEDs at one or both ends of the flexible circuit board. Since present linear fluorescent lamps are available in one, two, four, six, and eight feet lengths, the flexible circuit board can be designed in increments of one-foot lengths. Individual flexible circuit boards can be cascaded and connected in series to achieve the desired lengths. Likewise, the main outer tubular housing in linear form will be available in the desired lengths, i.e. one, two, four, six, and eight feet lengths. The main outer tubular housing can also be provided in a U-shape, circular, spiral shape, or other curved configuration. The slits provided on the flat flexible circuit board located between each linear array of LEDs allows for the rolled frame to contour and adapt its shape to fit into the curvature of the main outer tubular housing. Such a design allows for the versatile use in almost any shape that the main outer tubular housing can be manufactured in. There is an optional flexible center support that can isolate the integral electronics from the flexible circuit board containing the compact LED array, which may serve as a heat sink to draw heat away from the circuit board and LEDs to the center of the main outer tubular housing and thereby dissipating the heat at the two lamp base ends. There may be cooling holes or air holes on either lamp base end caps of the LED retrofit lamp, in the isolating flexible center support, and in the flexible circuit board containing the compact LED array to allow for proper cooling and airflow. In addition, the main outer tubular housing may contain small holes or other perforations to provide additional cooling of the power electronics, LEDs, and circuit board components. Each end cap of the LED retrofit lamp can terminate in single-pin or bi-pin contacts.
In another embodiment of the present invention, the array of discrete or surface mount LEDs are compactly arranged in a continuously long and thin LED array, and is fixedly mounted with lead-free solder onto a very long and thin flexible circuit board strip made of a high-temperature polyimide or equivalent material. The entire flexible circuit board with the attached LEDs is then spirally wrapped around an optional interior flexible center support. Because the center support is also made of a flexible material like rubber, etc. it can be formed into the shape of a U, a circle, or even into a helical spiral similar to existing CFL or compact fluorescent lamp shapes. The entire generally cylindrical assembly consisting of the compact strip of flexible circuit board spiraling around the center support is then inserted into the main outer tubular housing. Although this embodiment describes a generally cylindrical assembly, it can be appreciated by someone skilled in the art to form the flexible circuit board strip into shapes other than a cylinder, such as an elongated oval, triangle, rectangle, hexagon, octagon, etc. Accordingly, the shape of the tubular housing holding the individual flexible circuit board strip can be made in a similar shape to match the shape of the formed flexible circuit board strip assembly. The length of the entire assembly is always within the length of the main outer tubular housing. AC power generated by the external fluorescent ballasts is converted to DC power by additional integral electronics. Electrical connector means are used to connect the integral electronics to the light emitting diode arrays to provide current to the LEDs at one or both ends of the flexible circuit board. Since present linear fluorescent lamps are available in one, two, four, six, and eight feet lengths, the flexible circuit board can be designed in increments of one-foot lengths. Individual flexible circuit boards can be cascaded and connected in series to achieve the desired lengths. Likewise, the main outer tubular housing in linear form will be available in the desired lengths, i.e. one, two, four, six, and eight feet lengths. Although this embodiment can be used for linear lamps, it can be appreciated by someone skilled in the art for use with curved tubular housings as well. Here, the flexible and hollow center support isolates the integral electronics from the flexible circuit board containing the compact LED array. It can be made of heat conducting material that can also serve as a heat sink to draw heat away from the circuit board and LEDs to the center of the main outer tubular housing and thereby dissipating the heat at the two lamp base ends. There may be cooling holes or air holes on either lamp base end caps of the LED retrofit lamp, in the isolating flexible center support, and in the flexible circuit board containing the compact LED array to allow for proper cooling and airflow. In addition, the main outer tubular housing may contain small holes or other perforations to provide additional cooling of the power electronics, LEDs, and circuit board components. Each end cap of the LED retrofit lamp can terminate in single-pin or bi-pin contacts.
In yet another embodiment of the present invention, the leads of each discrete LED is bent at a right angle and then compactly arranged and fixedly mounted with lead-free solder along the periphery of a generally round, flat, and rigid circuit board disk. Although this embodiment describes a generally round circular circuit board disk, it can be appreciated by someone skilled in the art to use circuit boards or support structures made in shapes other than a circle, such as an oval, triangle, rectangle, hexagon, octagon, etc. Accordingly, the shape of the tubular housing holding the individual circuit boards can be made in a similar shape to match the shape of the circuit boards. The circuit board disks are manufactured out of G10 epoxy material, FR4, or other equivalent rigid material. The LEDs in each rigid circuit board disk can be mounted in a direction perpendicular to the rigid circuit board disk, which results in light emanating in a direction perpendicular to the rigid circuit board disk instead of in a direction parallel to the circuit board as described in the previous embodiments. It can also be appreciated by someone skilled in the art to use one or more side emitting LEDs mounted directly to one side of the rigid circuit board disks with adequate heat sinking applied to the LEDs on the same or opposite sides of the rigid circuit board disks. The side emitting LEDs will be mounted in a direction parallel to the rigid circuit board disk, which also results in light emanating in a direction perpendicular to the rigid circuit board disk instead of in a direction parallel to the circuit board as described in the previous embodiments. Each individual rigid circuit board disk is then arranged one adjacent another at preset spacing by grooves provided on the inside surface of the main outer tubular housing that hold the outer rim of the individual circuit boards. The individual circuit boards are connected by electrical transfer means including headers, connectors, and/or discrete wiring that interconnect all the individual LED arrays to two lamp base caps at both ends of the tubular housing. The entire assembly consisting of the rigid circuit board disks with each LED array is inserted into one half of the main outer tubular housing. The main outer tubular housing here can be linear, U-shaped, or round circular halves. Once all the individual rigid circuit board disks and LED arrays are inserted into the grooves provided on the one half of the main outer tubular housing and are electrically interconnected to each other and to the two lamp base ends, the other mating half of the main outer tubular housing is snapped over the first half to complete the entire LED retrofit lamp assembly. The length of the entire assembly is always within the length of the main outer tubular housing. AC power generated by the external fluorescent ballasts is converted to DC power by additional integral electronics. Electrical connector means are used to connect the integral electronics to the light emitting diode arrays to provide current to the LEDs at both ends of the complete arrangement of rigid circuit board disks. Since present linear fluorescent lamps are available in one, two, four, six, and eight feet lengths, the rigid circuit board disks can be stacked to form increments of one-foot lengths. Individual rigid circuit board disks can be cascaded and connected in series to achieve the desired lengths. Likewise, the main outer tubular housing in linear form will be available in the desired lengths, i.e. one, two, four, six, and eight feet lengths. Again, this last described embodiment can be used for linear lamps, but it is also suited for curved tubular housings. There may be cooling holes or air holes on either base end caps of the improved LED lamp, and in the individual rigid circuit board disks containing the compact LED array to allow for proper cooling and airflow. In addition, the main outer tubular housing may contain small holes or other perforations to provide additional cooling of the power electronics, LEDs, and circuit board components. Each end cap of the LED retrofit lamp can terminate in single-pin or bi-pin contacts.
It can be appreciated by someone skilled in the art to use a lesser amount of LEDs in the circuit board configurations to project light from an existing fluorescent fixture in the general direction out of the fixture only without any light projected back into the fixture itself This will allow for lower power consumption, material costs, and will offer greater fixture efficiencies with reduced light losses.
Ballasts are usually connected to an AC (alternating current) power line operating at 50 Hz or 60 Hz (hertz or cycles per second) depending on the local power company. Most ballasts are designed for one of these frequencies, but not both. Some electronic ballast, however, can operate on both frequencies. Also, some ballasts are designed to operate on DC (direct current) power. These are considered specialty ballasts for applications like transportation vehicle bus lighting.
Electromagnetic and hybrid ballasts operate the lamp at the same low frequency as the power line at 50 Hz or 60 Hz. Electronic ballasts operate the lamp at a higher frequency at or above 20,000 Hz to take advantage of the increased lamp efficiency. The fluorescent lamp provides roughly 10% more light when operating at high frequency versus low frequency for the same amount of input power. The typical application, however involves operating the fluorescent lamp at lower input power and high frequency while matching the light output of the lamp at rated power and low frequency. The result is a substantial savings in energy conservation.
Ballasts can be connected or wired between the input power line and the lamp in a number of configurations. Multiple lamp ballasts for rapid start or instant start lamps can operate lamps connected in series or parallel depending on the ballast design. When lamps are connected in series to a ballast and one lamp fails, or is removed from the fixture, the other lamp(s) connected to that ballast would not light. When the lamps are connected in parallel to a ballast and one lamp fails, or are removed, the other lamp(s) will continue to light.
As discussed earlier, electronic rapid start fluorescent lamp ballasts apply a low voltage of about 4 volts across the two contact pins at each end of the lamp. After this voltage is applied for at least one half of a second, a high voltage arc is struck across the lamp by the ballast starting voltage. After the lamp ignites, the arc voltage is reduced down to a proper operating voltage and the current is limited through the lamp by the ballast. In the case of electronic instant start fluorescent lamp ballasts, an initial high-voltage arc is struck between the two lamp base ends to ignite the lamp. After the lamp ignites, the arc voltage is again reduced down to a proper operating voltage and the current is limited through the lamp by the ballast. For magnetic type lamp ballasts, a constant voltage is applied to the two lamp base ends to energize and maintain the electrical arc within the fluorescent lamp.
For standard fluorescent lamps with a filament voltage of about 3.4 volts to 4.5 volts, the minimum starting voltage to ignite the lamp can range from about 108 volts to about 230 volts. For HO or high output fluorescent lamps, the minimum starting voltage is higher from about 110 volts to about 500 volts.
Given these various voltage considerations, the present invention is designed to work with all existing ballast output configurations. The improved LED lamp does not require the pre-heating of a filament like a fluorescent lamp and does not need the ignition voltage to function. The circuit is designed so that the electrical contact pins of the two lamp base end caps of the LED retrofit lamp may be reversed, or the entire lamp assembly can be swapped end for end and still function correctly similar to a fluorescent lamp. In the preferred electrical design, a single LED circuit board array can be powered by two separate power electronics at either end of the improved LED lamp consisting of bridge rectifiers to convert the AC voltage to DC voltage. Voltage surge absorbers are used to limit the high voltage to a workable voltage, and optional resistor(s) may be used to limit the current seen by the LEDs. The current limiting resistor(s) is purely optional, because the existing fluorescent ballast is already a current limiting device. The resistor(s) then serve as a secondary protection device. In a normal fluorescent lamp and ballast configuration, the ignition voltage travels from one end of the lamp to the other end. In the new and improved LED retrofit lamp, the common or lower potential of both circuits are tied together, and the difference in potential between the two ends will serve as the main direct current or DC voltage potential to drive the LED circuit board array. That is the anode will be the positive potential and the cathode will be the negative potential to provide power to the LEDs. The individual LEDs within the LED circuit board array can be electrically connected in series, in parallel, or in a combination of series and/or parallel configurations.
In an alternate electrical design for electronic rapid start ballasts; the LED lamp can be electronically designed to work with the initial filament voltage of four volts present on one end of the LED lamp while leaving the other end untouched. The filament voltage is converted through a rectifier circuit or an ac-to-dc converter circuit to provide a DC or direct current voltage to power the LED array. In-line series resistor(s) and/or transistors can be used to limit the current as seen by the LEDs. In addition, a voltage surge absorber or transient voltage suppresser device can be used on the AC input side of the circuit to limit the AC voltage driving the power converter circuit. This electrical design can be used for other types of ballasts as well.
In yet another alternate electrical design for existing fluorescent ballasts, both ends of the improved LED lamp will have a separate rectifier circuit or ac-to-dc converter circuit as described above. Again, the series resistor(s) and voltage surge absorber(s) can be used. In this arrangement, either end of the improved LED lamp will drive its own independent and separate LED circuit board array. This will allow the improved LED lamp to remain lit if one LED array tends to go out leaving the other on.
LEDs are now available in colors like Red, Blue, Green, Yellow, Amber, Orange, and many other colors including White. Although any type and color of LED can be used in the LED arrays used on the circuit boards of the present invention, a LED with a wide beam angle will provide a better blending of the light beams from each LED thereby producing an overall generally evener distribution of light output omni-directionally and in every position. The use of color LEDs eliminates the need to wrap the fluorescent lamp body in colored gel medium to achieve color dispersions. Color LEDs give the end user more flexibility on output power distribution and color mixing control. The color mixing controls are necessary to achieve the desired warm tone color temperature and output.
As an option, the use of a compact array of LEDs strategically arranged in an alternating hexagonal pattern provides the necessary increased number of LEDs resulting in a more even distribution and a brighter output. The minimum number of LEDs used in the array is determined by the total light output required to be at least equivalent to an existing fluorescent lamp that is to be replaced by the improved LED lamp of the present invention.
Besides using discrete radial mounted 5 mm or 10 mm LEDs, which are readily available from LED manufacturers including Nichia, Lumileds, Gelcore, etc. just to name a few, surface mounted device (SMD) light emitting diodes can be used in some of the embodiments of the present invention mentioned above.
SMD LEDs are semiconductor devices that have pins or leads that are soldered on the same side that the components sit on. As a result there is no need for feed-through hole passages where solder is applied on both sides of the circuit boards. Therefore, SMD LEDs can be used on single sided boards. They are usually smaller in package size than standard discrete component devices. The beam spread of SMD LEDs is somewhat wider than discrete axial LEDs, yet well less than 360-degree beam spread devices.
In particular, the Luxeon brand of white SMD (surface mounted device) LEDs can also be used. Luxeon is a product from Lumileds Lighting, LLC a joint venture between Philips Lighting and Hewlett Packard""s Agilent Technologies. Luxeon power light source solutions offer huge advantages over conventional lighting and huge advantages over other LED solutions and providers. Lumileds Luxeon technology offers a 17 lumens 1-Watt white LED in an SMD package that operates at 350 mA and 3.2 volts DC, as well as a high flux 120 lumens 5-Watt white LED in a lambertian or a side emitting radiation pattern SMD package that operates at 700 mA and 6.8 volts. Nichia Corporation offers a similarly packaged white output LED with 23 lumens also operating at 350 mA and 3.2 volts. LEDs will continue to increase in brightness within a relatively short period of time.
In addition, Luxeon now markets a new Luxeon Emitter SMD high-brightness LED that has a special lens in front that bends the light emitted by the LED at right angles and projects the light beam radially perpendicular to the LED center line so as to achieve a light beam having a 360 degree radial coverage. In addition, such a side-emitting radial beam SMD LED has what is designated herein as a high-brightness LED capacity.
The described LED retrofit lamp invention can be manufactured in variety of different fluorescent lamp bases, including, but not limited to medium bi-pin base, single-pin base, recessed double contact (DC) base, circline pin base, and PL (bi-pin) base and medium screw base used with compact fluorescents.
The present invention will be better understood and the objects and important features, other than those specifically set forth above, will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawings, describes, illustrates, and shows preferred embodiments or modifications of the present invention, and what is presently considered and believed to be the best mode of practice in the principles thereof.